26 May 2011

Faraday waves generated by an alligator's scutes

I would advise locating your mute button before watching the video, in order to avoid the inane chatter that accompanies the interesting video.  Here's some better info:
Faraday waves, also known as Faraday ripples, named after Michael Faraday, are nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. When the vibration frequency exceeds a critical value, the flat hydrostatic surface becomes unstable...

If a layer of liquid is placed on top of a vertically oscillating piston, a pattern of standing waves appears which oscillates at half the driving frequency... The waves can take the form of stripes, close-packed hexagons, or even squares or quasiperiodic patterns. Faraday waves are commonly observed as fine stripes on the surface of wine in a wineglass that is ringing like a bell. Faraday waves also explain the 'fountain' phenomenon on a singing bowl.
And, as a bonus: "Alligators are the only non-avian species shown to have one-way breathing":
"...we show that air flows unidirectionally through parabronchi in the lungs of the American alligator, an amphibious ectotherm without air sacs, which suggests that this pattern dates back to the basal archosaurs of the Triassic and may have been present in their nondinosaur descendants (phytosaurs, aetosaurs, rauisuchians, crocodylomorphs, and pterosaurs) as well as in dinosaurs."
Two things I didn't know in one article; this is a good morning.

Via Wired Science, which has some explanation re the generation of the Faraday waves -
Three centimeters is also almost exactly one-third the distance between the rough protrusions, or scutes, on the creature’s back. “We think that the shape of their scutes helps them create these waves..."

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